JP6037221B2 - Wide angle lens, imaging lens unit, imaging device and information device - Google Patents

Description

  The present invention relates to a wide-angle lens, an imaging lens unit, and an information device that can be used as an imaging lens in a digital camera, a video camera, an in-vehicle camera, a surveillance camera, a portable information terminal device, and the like.

In recent years, automobiles equipped with in-vehicle cameras and surveillance cameras have become widespread. In-vehicle cameras, surveillance cameras, and the like are required to have super wide-angle lenses with a horizontal angle of view exceeding 90 degrees. In addition, a lens having a resolving power corresponding to an image sensor with more than 1 million pixels is required to acquire a high-definition image.
Furthermore, imaging devices such as in-vehicle cameras and surveillance cameras are often used in environments with large environmental fluctuations, including outdoors, and it is important that the optical performance of the imaging optical system is stable against environmental fluctuations. is there.
As such a wide-angle vehicle-mounted camera or surveillance camera, an ultra-wide-angle lens described in Patent Document 1 (Patent No. 2992547), an imaging lens described in Patent Document 2 (Japanese Patent Laid-Open No. 2010-009028), or a patent A super-wide-angle lens described in Document 3 (Japanese Patent Laid-Open No. 2002-072085) is known.
However, the super wide-angle lens described in Patent Document 1 is composed entirely of spherical lenses, has a large overall length, and has restrictions in use.
The imaging lens described in Patent Document 2 is an imaging element in which the number of plastic lenses is five out of six lenses and the total number is small, but the maximum image height is 2.4 and exceeds 1 million pixels. It is difficult to cope with.
The imaging lens described in Patent Document 3 is configured by using one plastic lens among six lenses, and the total length is small, but the maximum image height is 2.25, which exceeds 1 million pixels. It is difficult to cope with an image sensor.
In any of the patent documents, no special consideration is given to environmental fluctuations.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a compact wide-angle lens having high resolving power.

In order to achieve the above-described object, the wide-angle lens according to the invention described in claim 1
In order from the object side to the image side, a front group lens, an optical diaphragm, and a rear group lens are configured. The front group lens is sequentially arranged from the object side to the image side, a meniscus negative first lens, and plastic. A negative second lens having an aspherical surface and a positive third lens, and the rear lens group is a positive fourth lens, a positive fifth lens, and a negative sixth lens in order from the object side to the image side. A wide-angle lens composed of a positive seventh lens made of plastic and having an aspheric surface ,
Of the four positive lenses, two positive glass lenses satisfy the following conditional expression (1):
−3.7 × 10 ⁻⁶ <dN / dT <−2.2 × 10 ⁻⁶ (1)
However, dN / dT represents the refractive index change rate of the d-line with respect to the temperature change near room temperature.

According to the wide-angle lens according to the invention of claim 1,
In order from the object side to the image side, a front group lens, an optical diaphragm, and a rear group lens are configured. The front group lens is sequentially arranged from the object side to the image side, a meniscus negative first lens, and plastic. A negative second lens having an aspherical surface and a positive third lens, and the rear lens group is a positive fourth lens, a positive fifth lens, and a negative sixth lens in order from the object side to the image side. The lens is composed of a positive seventh lens made of plastic and having an aspheric surface, and the change in refractive index of the d-line with respect to the temperature change near room temperature is defined as dN / dT
Of the four positive lenses, two positive glass lenses have the following conditional expression (1),
−3.7 × 10 ⁻⁶ <dN / dT <−2.2 × 10 ⁻⁶ (1)
By satisfying
Each aberration can be effectively corrected, and a high-resolution and compact wide-angle lens can be provided.

1 is a cross-sectional view along an optical axis showing a cross-sectional configuration of a wide-angle lens according to a first embodiment of the present invention and Example 1. FIG. FIG. 2 is an aberration curve diagram showing spherical aberration, astigmatism, and distortion of the wide-angle lens according to Example 1 of the present invention shown in FIG. 1. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 1 of this invention shown in FIG. FIG. 6 is a cross-sectional view along the optical axis showing a configuration of a wide-angle lens according to a second embodiment of the present invention and Example 2. FIG. 5 is an aberration curve diagram showing spherical aberration, astigmatism and distortion of the wide-angle lens according to Example 2 of the present invention shown in FIG. 4. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 2 of this invention shown in FIG. FIG. 6 is a cross-sectional view along the optical axis showing a cross-sectional configuration of a wide-angle lens according to Example 3 of the third embodiment of the present invention. FIG. 9 is an aberration curve diagram showing spherical aberration, astigmatism and distortion of the wide-angle lens according to Example 3 of the present invention shown in FIG. 7. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 3 of this invention shown in FIG. FIG. 10 is a cross-sectional view along the optical axis showing the configuration of a wide-angle lens according to Example 4 of the present invention. FIG. 11 is an aberration curve diagram showing spherical aberration, astigmatism, and distortion of the wide-angle lens according to Example 4 shown in FIG. 10. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 4 of this invention shown in FIG. FIG. 9 is a cross-sectional view along the optical axis showing a cross-sectional configuration of a wide-angle lens according to a fifth embodiment of the present invention. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism and distortion of the wide-angle lens according to Example 5 shown in FIG. 13. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 5 of this invention shown in FIG. FIG. 10 is a cross-sectional view along the optical axis showing the configuration of a wide-angle lens according to Example 6 of the sixth embodiment of the present invention. FIG. 17 is an aberration curve diagram showing spherical aberration, astigmatism, and distortion of the wide-angle lens according to Example 6 illustrated in FIG. 16. It is an aberration curve figure which shows the coma aberration of the wide angle lens by Example 6 of this invention shown in FIG. It is the perspective view seen from the object side which shows typically the appearance composition of one embodiment of a digital camera as an imaging device concerning the present invention. It is the perspective view seen from the photographer side which shows typically the external appearance structure of the digital camera of FIG. It is a block diagram which shows typically the function structure of the digital camera of FIG. 19 and FIG.

Hereinafter, based on an embodiment of the present invention, a wide angle lens, an imaging lens unit, an imaging device, and an information device according to the present invention will be described in detail with reference to the drawings.
That is, FIG. 1 shows the first embodiment of the present invention, and at the same time, the wide-angle lens according to Example 1 based on specific numerical values.
Before describing examples including specific numerical values, first, a fundamental embodiment of the present invention will be described.
The wide-angle lens according to the present invention is characterized by a front lens group, an optical aperture, and a rear lens group in order from the object side to the image side. The front lens group is directed from the object side to the image side. A negative first lens having a meniscus shape, a negative second lens having an aspherical surface, and a positive third lens. The rear lens group has a positive first lens in order from the object side to the image side. 4 lens, a positive fifth lens, a negative sixth lens made of plastic, Ru near that and a positive seventh lens having an aspherical surface.

In the configuration of the present invention, a negative meniscus lens having a convex surface facing the object side is disposed as the first lens closest to the object side of the front group lens, and a negative aspheric lens is disposed as the second lens. With such an arrangement, a light beam having a half angle of view close to 90 degrees is gradually bent to guide the light beam to the image sensor, and a first lens and a second lens having a strong negative power are arranged closer to the object side than the optical aperture. Back focus is secured by using retro focus. By arranging the positive third lens on the image side of the negative second lens, spherical aberration, axial chromatic aberration and lateral chromatic aberration generated in the front lens group are corrected.
A positive fourth lens is arranged on the most object side of the rear lens group, and a positive fifth lens is arranged on the image side of the fourth lens, so that light beams diverged by the first lens and the second lens are gradually collected. Light and suppress the generation of spherical aberration. In addition, the fifth lens, the sixth lens, and the seventh lens are arranged in a positive-negative-positive symmetrical arrangement to correct aberrations in a balanced manner, and an aspherical lens is used as the most positive image-side seventh lens. This effectively corrects spherical aberration, coma and astigmatism.
The present invention further has the following features.

The wide-angle lens according to the present invention preferably has two positive lenses that satisfy the following conditional expression (1) under the above configuration (corresponding to claim 1 ).
−3.7 × 10 ⁻⁶ <dN / dT <−2.2 × 10 ⁻⁶ (1)
However, dN / dT represents the refractive index change rate of the d-line with respect to the temperature change near room temperature.
Plastic aspheric lenses can be reduced in cost and weight compared to glass aspheric lenses.
However, the plastic lens has a larger refractive index temperature change (hereinafter referred to as dN / dT) and a linear expansion coefficient than the glass lens, and the back focus tends to fluctuate with the temperature change. In general, a plastic lens has a negative dN / dT, and the refractive index decreases as the temperature increases, and the refractive index increases as the temperature decreases. Therefore, if a plastic lens is used for the lens with strong negative power of the front lens group, the negative power becomes weak when the temperature rises, so the back focus moves greatly to the object side, and the negative power becomes strong when the temperature drops. The back focus moves greatly to the image side.
In order to correct the back focus fluctuation due to the temperature of the negative plastic lens with glass, glass having a negative dN / dT may be used for the positive lens.

In the present embodiment, the negative plastic lens has a strong power, and by using two glasses having negative d-line refractive index change rates dN / dT, the negative plastic lens has a temperature change. Effectively corrects back focus fluctuation.
When only one glass having a negative d-line refractive index change rate dN / dT is used, it is necessary to reduce the refractive power of the negative plastic lens in order to reduce the fluctuation amount of the back focus. It is not desirable because it is disadvantageous. Furthermore, the temperature characteristic of a negative plastic lens cannot be corrected with a single glass having a negative refractive index change rate dN / dT.
When the upper limit of the conditional expression (1) is exceeded, the back focus fluctuation amount due to the temperature change of the positive glass lens becomes small, and the back focus fluctuation of the negative plastic lens cannot be corrected.
On the other hand, if the lower limit of conditional expression (1) is not reached, the fluctuation of the back focus of the positive glass lens becomes excessively large, which is not preferable because the back focus is overcorrected.
Desirably, the following conditional expression (2) should be satisfied (corresponding to claims 2 and 3 ).
−0.9 <fn / fp <−0.7 (2)
Here, fn represents the focal length of a negative plastic lens having an aspheric surface, and fp represents the focal length of a positive plastic lens having an aspheric surface.

The back focus fluctuations due to temperature changes are opposite to each other between the negative plastic lens and the positive plastic lens. Therefore, by appropriately setting the power of the negative plastic lens and the positive plastic lens as in the conditional expression (2), it is possible to reduce the back focus fluctuation due to the temperature change. Furthermore, the conditional expression (1) is satisfied, and the conditional expression (2) is satisfied, whereby the back focus fluctuation can be reduced more effectively.
When the upper limit of conditional expression (2) is exceeded, the power of the negative plastic lens becomes larger than the power of the positive plastic lens. Therefore, the back focus moves greatly toward the object side due to the temperature rise, and the back focus is lowered due to the temperature fall. It moves greatly to the image plane side.
If the lower limit of conditional expression (2) is not reached, the power of the positive plastic lens becomes larger than the power of the negative plastic lens. Moves greatly to the object side.
More preferably, the following conditional expression (3) should be satisfied (corresponding to claim 4).
-2.3 <fn / f < -1.8 (3)
However, fn represents the focal length of a negative plastic lens having an aspheric surface, and f represents the focal length of the entire system.

If the upper limit of conditional expression (3) is exceeded, the negative power of the second lens becomes weak and the spherical aberration becomes insufficiently corrected, which is not desirable.
If the lower limit of conditional expression (3) is not reached, the negative power of the second lens becomes strong and the spherical aberration is overcorrected, which is not desirable. Furthermore, since aberration variation due to the eccentricity of the second lens tends to increase, it is not preferable to give the second lens too much power.
More preferably, the following conditional expression (4) should be satisfied (corresponding to claim 5).
1.6 <H2 / R2 <1.8 (4)
However, H2 represents the effective diameter on the image side surface of the negative first lens, and R2 represents the radius of curvature of the image side surface of the negative first lens.
By setting the conditional expression (4) within an appropriate range, the ease of manufacturing the first lens is secured and the performance is secured.
When the upper limit of conditional expression (4) is exceeded, the radius of curvature of the image side surface of the first lens becomes too small, making manufacturing difficult.
If the lower limit of conditional expression (4) is not reached, the curvature radius of the image side surface of the first lens becomes too large, which is disadvantageous for widening the angle.

Further, it is desirable that the positive fifth lens and the negative sixth lens are cemented lenses and satisfy the following conditional expression (5) (corresponding to claim 6).
-4.0 <fc / fR <-1.9 (5)
However, fc represents the focal length of the cemented lens composed of the positive fifth lens and the negative sixth lens, and fR represents the focal length of the rear lens group.
The fifth lens and the sixth lens are used as a cemented lens, and the cemented lens has negative power. The power arrangement of the rear lens group is positive / negative / positive, so-called triplet type. Furthermore, the axial chromatic aberration and the lateral chromatic aberration are effectively corrected by configuring the cemented lens having negative power with a cemented lens of a positive lens and a negative lens.
When the upper limit of conditional expression (5) is exceeded, the power of the negative cemented lens becomes strong, and the performance change due to decentration becomes large. Furthermore, the light beam is greatly bent by the cemented lens, and the performance change due to the variation in the surface distance between the cemented lens and the seventh lens also becomes undesirably large.

  If the lower limit of conditional expression (5) is not reached, the power of the negative cemented lens becomes weak, which is undesirable for correction of spherical aberration and chromatic aberration.

Furthermore, it is desirable to satisfy the following conditional expression (6) (corresponding to claim 7).
−1.3 <f12 / f <−1.0 (6)
However, f12 represents the combined focal length of the first lens and the second lens, and f represents the focal length of the entire system.
Exceeding the upper limit of conditional expression (6) is undesirable because the negative power of the front lens group becomes too strong and the manufacturing error sensitivity becomes strong. In addition, the radius of curvature of the lens becomes small, making it difficult to manufacture the lens.
If the lower limit of conditional expression (6) is not reached, the negative power of the front lens group becomes too weak, and the light beam cannot be bent greatly, which is disadvantageous for widening the angle.
Further, by using a wide-angle lens configured using the wide-angle lens as shown in the above embodiment as an imaging lens, it can be used for an imaging lens unit, an imaging device, and an information device.
Therefore, each aberration can be effectively corrected, and a high-resolution and compact imaging apparatus or information apparatus can be realized.

In addition, the meaning of the symbol in Example 1- Example 6 is as follows.
f: Focal length of the entire system F: F value (F number)
ω: Half angle of view R: Radius of curvature (Paraxial radius of curvature for aspheric surfaces)
D: surface interval Nd: refractive index [nu] d: Abbe number K: aspherical conic constant A _4: 4-order aspherical coefficients A _6: 6-order aspherical coefficients A _8: 8-order aspherical coefficients A _10: 10 The following aspheric coefficient A ₁₂ : 12th-order aspheric coefficient where the aspherical surface used here is C when the reciprocal of the paraxial radius of curvature (paraxial curvature) is H and the height from the optical axis is H, An aspherical surface is defined by the following equation (7), where A _2i is the amount of displacement in the optical axis direction from the surface vertex.

FIG. 1 is a cross-sectional view along the optical axis of the optical system of the wide-angle lens according to the first embodiment of the present invention and Example 1. FIG. In FIG. 1 showing the lens group arrangement of Example 1, the left side in the figure is the object (subject) side.
That is, the wide-angle lens 1 according to the first embodiment of the present invention and Example 1 has a two-group configuration as shown in FIG. 1, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a convex surface having a positive refractive power and a larger curvature than the object side surface. The third lens L3 is a convex lens.

The rear lens group G2, in order from the object side to the image side, has a positive refractive power, and a fourth lens L4 composed of a biconvex lens having a convex surface with a larger curvature than the object side surface on the image side, and a positive lens And a fifth lens L5 composed of a biconvex lens having a convex surface with a larger curvature than the object-side surface on the image side, and a negative refractive power and a curvature on the object side that is larger than that of the image-side surface. The sixth lens L6 is composed of a biconcave lens having a large concave surface, and the seventh lens L7 is composed of a biconvex lens having positive refractive power and a convex surface having a larger curvature than the image side surface on the object side. Of these, the fifth lens L5 and the sixth lens L6 are intimately bonded to each other and integrally joined to form a two-lens cemented lens L5-L6. The seventh lens L7 is made of plastic and has both aspheric surfaces.
In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A material (referred to as a hybrid aspherical surface, a replica aspherical surface, etc.) can be used, but in this embodiment, a plastic molded aspherical surface is used.
An optical aperture AP is disposed between the front group lens G1 and the rear group lens G2, and a parallel plate FT disposed on the image plane side of the rear group lens G2 is an optical low-pass filter, an infrared cut filter, or the like. A parallel plate equivalent to these is shown assuming various filters and a cover glass (shield glass) of a light receiving element such as a CCD sensor.

The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.
Further, when used for a surveillance camera, an in-vehicle camera, etc., it may be set (fixed) to an infinite distance or a predetermined target distance.
FIG. 1 also shows the surface numbers of the optical surfaces. Note that each reference symbol in FIG. 1 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol. Therefore, a reference symbol common to the drawings according to the other embodiments. Even if attached, they are not necessarily in common with other embodiments.
The optical characteristics of each optical element in Example 1, that is, the radius of curvature R, the surface interval D, the refractive index Nd, and the Abbe number νd are as shown in Table 1 below.
Moreover, all the optical glasses used are "made by OHARA Co., Ltd.", all the plastic lenses used are "made by Nippon Zeon Co., Ltd.", and the glass type name is each trade name.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 1, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical third surface
K = 26.5265376874132
A4 = -2.72437E-04
4th page
K = -9.90314E-01
A4 = 1.08123E-02
A6 = 9.51994E-04
A8 = 1.29549E-04
13th page
K = 0
A4 = -4.94681E-03
A6 = 3.16998E-05
14th page
K = 0
A4 = -1.70011E-03
A6 = -1.02760E-04
A8 = 8.35288E-06
Here, E-n represents a power of 10. The values corresponding to the conditional expressions (1) to (6) in the above-described first embodiment are as shown in the following Table 2, and the conditional expressions (1) to (6) respectively. Conditional expression (6) is satisfied.

  2 and 3 show respective aberration diagrams of the spherical aberration, astigmatism, distortion aberration, and coma aberration of Example 1. FIG. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

FIG. 4 is a cross-sectional view along the optical axis of the optical system of the wide-angle lens according to the second embodiment of the present invention and Example 2. In FIG. 4 showing the lens group arrangement of the second embodiment, the left side in the figure is the object (subject) side.
That is, the wide-angle lens 2 according to the second embodiment of the present invention and Example 2 has a two-group configuration as shown in FIG. 4, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a third lens L3 made of a positive meniscus lens having positive refractive power and a convex surface facing the image side It consists of and.

The rear lens group G2 has a positive refractive power in order from the object side to the image side, and has a positive refractive power, and a fourth lens L4 composed of a positive meniscus lens having a convex surface facing the image side, A fifth lens L5 composed of a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side, and a biconcave lens having negative refractive power and a concave surface having a larger curvature than the image side surface on the object side And a seventh lens L7 having a positive refracting power and a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and of these, the fifth lens L5 and the sixth lens L6 are closely bonded and bonded together to form a two-lens cemented lens L5-L6 cemented lens. The seventh lens L7 is made of plastic and has both aspheric surfaces.
In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A material (referred to as a hybrid aspherical surface, a replica aspherical surface, etc.) can be used, but in this embodiment, a plastic molded aspherical surface is used.
An optical aperture AP is disposed between the front group lens G1 and the rear group lens G2, and a parallel plate FT disposed on the image plane side of the rear group lens G2 is an optical low-pass filter, an infrared cut filter, or the like. A parallel plate equivalent to these is shown assuming various filters and a cover glass (shield glass) of a light receiving element such as a CCD sensor.

The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.
Further, when used for a surveillance camera, an in-vehicle camera, etc., it may be set (fixed) to an infinite distance or a predetermined target distance.
FIG. 4 also shows the surface numbers of the optical surfaces. Note that each reference symbol in FIG. 4 is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference symbol, and therefore, a reference symbol common to the drawings according to other embodiments. Even if attached, they are not necessarily in common with other embodiments.
The optical characteristics of each optical element in Example 2, that is, the radius of curvature R, the surface interval D, the refractive index Nd, and the Abbe number νd are as shown in Table 3 below.

In Table 3, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 3, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical third surface
K = 2.34498E + 01
A4 = -5.54639E-04
A6 = -6.60182E-06
A8 = 9.97683E-07
A10 = -1.60420E-08

4th page
K = -7.76224E-01
A4 = 1.04301E-02
A6 = 1.02833E-03
A8 = 1.82521E-04
A10 = 3.11699E-06
A12 = 1.61475E-06
13th page
K = 0
A4 = -5.05053E-03
A6 = 9.35629E-05
14th page
K = 0
A4 = -2.23082E-03
A6 = -3.49569E-05
A8 = 7.04152E-06
Here, E-n represents a power of 10.
Values corresponding to the conditional expressions (1) to (6) in Example 2 described above are as shown in the following Table 4, and satisfy the conditional expressions (1) to (6), respectively.

  5 and 6 show aberration diagrams of the spherical aberration, astigmatism, distortion aberration, and coma aberration of Example 2, respectively. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

FIG. 7 is a cross-sectional view along the optical axis of the optical system of the wide-angle lens according to the third embodiment of the present invention and Example 3. In FIG. 7 showing the arrangement of the lens groups of Example 3, the left side in the figure is the object (subject) side.
That is, the wide-angle lens 3 according to the third embodiment of the present invention and according to Example 3 has a two-group configuration as shown in FIG. 7, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a flat surface having a positive refractive power and a convex surface having a larger curvature than the object side surface. The third lens L3 is a convex lens.

The rear lens group G2 has a positive refractive power in order from the object side to the image side, and has a positive refractive power, and a fourth lens L4 composed of a positive meniscus lens having a convex surface facing the image side, A fifth lens L5 composed of a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side, and a biconcave lens having negative refractive power and a concave surface having a larger curvature than the image side surface on the object side And a seventh lens L7 having a positive refracting power and a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and of these, the fifth lens L5 and the sixth lens L6 are closely bonded and bonded together to form a two-lens cemented lens L5-L6 cemented lens. The seventh lens L7 is made of plastic and has both aspheric surfaces.
In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A material (referred to as a hybrid aspherical surface, a replica aspherical surface, etc.) can be used, but in this embodiment, a plastic molded aspherical surface is used.

An optical aperture AP is disposed between the front group lens G1 and the rear group lens G2, and a parallel plate FT disposed on the image plane side of the rear group lens G2 is an optical low-pass filter, an infrared cut filter, or the like. A parallel plate equivalent to these is shown assuming various filters and a cover glass (shield glass) of a light receiving element such as a CCD sensor.
The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.
Further, when used for a surveillance camera, an in-vehicle camera, or the like, the focus may be set (fixed) at an infinite distance or a predetermined target distance.
The optical characteristics of each optical element in Example 3, that is, the radius of curvature R, the surface interval D, the refractive index Nd, and the Abbe number νd are as shown in Table 5 below.

In Table 5, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 5, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical third surface
K = 2.39037E + 01
A4 = -2.86444E-04

4th page
K = -9.22645E-01
A4 = 1.10464E-02
A6 = 9.69189E-04
A8 = 2.30615E-04
13th page
K = 0
A4 = -4.68869E-03
A6 = 3.40890E-05
14th page
K = 0
A4 = -1.70442E-03
A6 = -1.02760E-04
A8 = 8.35288E-06
Here, E-n represents a power of 10.
Values corresponding to Conditional Expression (1) to Conditional Expression (6) in Example 3 described above are as shown in Table 6 below, and satisfy Conditional Expression (1) to Conditional Expression (6), respectively.

  FIGS. 8 and 9 show aberration diagrams of the spherical aberration, astigmatism, distortion aberration, and coma aberration of Example 3, respectively. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

FIG. 10 is a sectional view along the optical axis of the optical system of the wide-angle lens according to the fourth embodiment of the present invention and Example 4. In FIG. 10 showing the arrangement of the lens groups of Example 4, the left side in the figure is the object (subject) side.
That is, the wide-angle lens 4 according to the fourth embodiment of the present invention and according to Example 4 has a two-group configuration as shown in FIG. 10, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a convex surface having a positive refractive power and a larger curvature than the object side surface. The third lens L3 is a convex lens.

  The rear lens group G2, in order from the object side to the image side, has a positive refractive power, and a fourth lens L4 composed of a biconvex lens having a convex surface with a larger curvature than the object side surface on the image side, and a positive lens And a fifth lens L5 composed of a biconvex lens having a convex surface with a larger curvature than the object-side surface on the image side, and a negative refractive power and a curvature on the object side that is larger than that of the image-side surface. The sixth lens L6 is composed of a biconcave lens having a large concave surface, and the seventh lens L7 is composed of a biconvex lens having positive refractive power and a convex surface having a larger curvature than the image side surface on the object side. Of these, the fifth lens L5 and the sixth lens L6 are intimately bonded to each other and integrally joined to form a two-lens cemented lens L5-L6. The seventh lens L7 is made of plastic and has both aspheric surfaces.

In addition, as an aspheric lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface, or a thin resin layer molded on the surface of the glass lens, the surface of which is aspherical (Referred to as hybrid aspherical surface, replica aspherical surface, etc.) can be used, but in this embodiment, a plastic molded aspherical surface is used.
The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.
Further, when used for a surveillance camera, an in-vehicle camera, etc., it may be set (fixed) to an infinite distance or a predetermined target distance.
The optical characteristics of each optical element in Example 4, that is, the radius of curvature R, the surface interval D, the refractive index Nd, and the Abbe number νd are as shown in Table 7 below.

In Table 7, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 7, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspherical surfaces. It is as follows.
Aspherical third surface
K = 3.23812E + 01
A4 = -2.47482E-04

4th page
K = -5.00000E-01
A4 = 6.07049E-03
A6 = 2.02812E-03
A8 = -9.84357E-06
13th page
K = 0
A4 = -4.98963E-03
A6 = 3.69393E-05
14th page
K = 0
A4 = -2.00278E-03
A6 = -1.02760E-04
A8 = 8.35288E-06
Here, E-n represents a power of 10.

  Values corresponding to the conditional expressions (1) to (6) in the above-described fourth embodiment are as shown in the following Table 8, which respectively satisfy the conditional expressions (1) to (6).

  FIGS. 11 and 12 show respective aberration diagrams of the spherical aberration, astigmatism, distortion aberration and coma aberration of Example 4. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

FIG. 13 is a cross-sectional view along the optical axis of the optical system of the wide-angle lens according to Example 5 of the fifth embodiment of the present invention. In FIG. 13 showing the arrangement of the lens groups of Example 5, the left side in the figure is the object (subject) side.
That is, the wide-angle lens 5 according to the fifth embodiment of the present invention and Example 5 has a two-group configuration as shown in FIG. 13, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a third lens L3 made of a positive meniscus lens having positive refractive power and a convex surface facing the image side It consists of and.

The rear lens group G2 has a positive refractive power in order from the object side to the image side, and has a positive refractive power, and a fourth lens L4 composed of a positive meniscus lens having a convex surface facing the image side, A fifth lens L5 composed of a biconvex lens having a convex surface having a larger curvature than the object side surface on the image side, and a biconcave lens having a negative refractive power and a concave surface having a larger curvature than the object side surface on the image side And a seventh lens L7 having a positive refracting power and a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and of these, the fifth lens L5 and the sixth lens L6 are closely bonded and bonded together to form a two-lens cemented lens L5-L6 cemented lens. The seventh lens L7 is made of plastic and has both aspheric surfaces.
In addition, as an aspherical lens, optical glass or optical plastic molded (glass molded aspherical surface, plastic molded aspherical surface), or a thin resin layer is molded on the surface of the glass lens, and the surface is aspherical. A material (referred to as a hybrid aspherical surface, a replica aspherical surface, etc.) can be used, but in this embodiment, a plastic molded aspherical surface is used.

An optical aperture AP is disposed between the front group lens G1 and the rear group lens G2, and a parallel plate FT disposed on the image plane side of the rear group lens G2 is an optical low-pass filter, an infrared cut filter, or the like. A parallel plate equivalent to these is shown assuming various filters and a cover glass (shield glass) of a light receiving element such as a CCD sensor.
The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.
Further, when used for a surveillance camera, an in-vehicle camera, etc., it may be set (fixed) to an infinite distance or a predetermined target distance.
The optical characteristics of each optical element in Example 5, that is, the radius of curvature R, the surface spacing D, the refractive index Nd, and the Abbe number νd are as shown in Table 9 below.

In Table 9, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
That is, in Table 9, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical third surface
K = 3.24051E + 01
A4 = -2.47390E-04

4th page
K = -7.24409E-01
A4 = 1.03563E-02
A6 = 1.44428E-03
A8 = 2.82542E-04
13th page
K = 0
A4 = -5.32550E-03
A6 = 7.00152E-05
14th page
K = 0
A4 = -2.44428E-03
A6 = -1.02760E-04
A8 = 8.35288E-06
Here, E-n represents a power of 10. The values corresponding to the conditional expressions (1) to (6) in the fifth embodiment described above are as shown in Table 10 below, and the conditional expressions (1) to (10) Conditional expression (6) is satisfied.

  FIGS. 14 and 15 show aberration diagrams of the spherical aberration, astigmatism, distortion and coma aberration of Example 5, respectively. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

FIG. 16 is a sectional view taken along the optical axis of the optical system of the wide-angle lens according to the sixth embodiment of the present invention and Example 6. In FIG. 16 showing the arrangement of the lens groups in Example 6, the left side is the object (subject) side.
That is, the wide-angle lens 6 according to the sixth embodiment of the present invention and Example 6 has a two-group configuration as shown in FIG. 16, and sequentially from the object side to the image side. The front lens group G1, the optical aperture AP, and the rear lens group G2 are arranged to form an optical system that forms an optical image of the object.
The front group lens G1 includes a first lens L1, a second lens L2, and a third lens L3, and the rear group lens G2 includes a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens. L7.
The front lens group G1 has a negative refractive power in order from the object side to the image side, and has a negative refractive power, and a first lens L1 composed of a negative meniscus lens having a convex surface facing the object side, A second lens L2 made of a plastic negative meniscus lens having a convex surface facing the object side and aspheric surfaces on both surfaces, and a third lens L3 made of a positive meniscus lens having positive refractive power and a convex surface facing the image side It consists of and.

The rear lens group G2 has a positive refractive power in order from the object side to the image side, and has a positive refractive power, and a fourth lens L4 composed of a positive meniscus lens having a convex surface facing the image side, A fifth lens L5 composed of a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and a biconcave lens having a negative refractive power and a concave surface having a larger curvature than the object side surface on the image side And a seventh lens L7 having a positive refracting power and a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side, and of these, the fifth lens L5 and the sixth lens L6 are closely bonded and bonded together to form a two-lens cemented lens L5-L6 cemented lens. The seventh lens L7 is made of plastic and has both aspheric surfaces.
An optical aperture AP is disposed between the front group lens G1 and the rear group lens G2, and a parallel plate FT disposed on the image plane side of the rear group lens G2 is an optical low-pass filter, an infrared cut filter, or the like. A parallel plate equivalent to these is shown assuming various filters and a cover glass (shield glass) of a light receiving element such as a CCD sensor.
The front group lens G1 and the rear group lens G2 are supported by a common support frame or the like that is appropriate for each group. For focusing or the like, the front group lens G1 and the rear group lens G2 are moved together for each group or the light receiving element is moved. Also good.

Further, when used for a surveillance camera, an in-vehicle camera, etc., it may be set (fixed) to an infinite distance or a predetermined target distance.
The optical characteristics of each optical element in Example 6, that is, the radius of curvature R, the surface interval D, the refractive index Nd, and the Abbe number νd are as shown in Table 11 below.

In Table 11, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface.
In other words, in Table 11, the optical surfaces of the third surface, the fourth surface, the thirteenth surface, and the fourteenth surface marked with “*” are aspheric surfaces, and the parameters of each aspheric surface in the equation (7) are It is as follows.
Aspherical third surface
K = 3.23986E + 01
A4 = -2.47339E-04

4th page
K = -8.50128E-01
A4 = 9.75953E-03
A6 = 1.05434E-03
A8 = 2.08418E-04
13th page
K = 0
A4 = -4.79281E-03
A6 = 4.34133E-05
14th page
K = 0
A4 = -2.06742E-03
A6 = -1.02760E-04
A8 = 8.35288E-06
Here, E-n represents a power of 10.
Values corresponding to Conditional Expression (1) to Conditional Expression (6) in Example 6 described above are as shown in the following Table 12, which respectively satisfy Conditional Expression (1) to Conditional Expression (6).

  FIGS. 17 and 18 show aberration diagrams of spherical aberration, astigmatism, distortion and coma aberration in Example 6, respectively. In these drawings, the solid line in astigmatism represents sagittal, and the broken line represents meridional. In addition, the thin line and the thick line in the spherical aberration, astigmatism, and coma aberration diagrams respectively represent the g line and the d line. The same applies to the aberration diagrams of the other examples.

[Seventh Embodiment]
Next, as an imaging apparatus according to the seventh embodiment of the present invention configured by adopting the above-described wide-angle lens according to the first to sixth embodiments of the present invention as an imaging optical system. The digital camera will be described with reference to FIGS. FIG. 19 is a perspective view schematically showing the external appearance of the digital camera viewed from the front side which is the object side, that is, the subject side, and FIG. 20 is a schematic external view of the digital camera viewed from the back side which is the photographer side. FIG. 21 is a schematic block diagram showing a functional configuration of a digital camera. Here, the image pickup apparatus has been described by taking a digital camera as an example, but the wide-angle lens according to the present invention may be employed in a silver salt film camera that uses a silver salt film as a conventional image recording medium.
In addition, an information device such as a so-called PDA (personal data assistant) or a portable information terminal device such as a cellular phone in which a camera function is incorporated is widely used. Although such an information device also has a slightly different appearance, it includes substantially the same functions and configuration as a digital camera, and the zoom lens according to the present invention is adopted as an imaging optical system in such an information device. May be.

  As shown in FIGS. 19 and 20, the digital camera includes a photographing lens 101, an optical viewfinder 102, a strobe (flashlight) 103, a shutter button 104, a camera body 105, a power switch 106, a liquid crystal monitor 107, an operation button 108, a memory. A card slot 109 and the like are provided. Further, as shown in FIG. 21, the digital camera includes a central processing unit (CPU) 111, an image processing device 112, a light receiving element 113, a signal processing device 114, a semiconductor memory 115 and a communication card 116.

  The digital camera includes a photographing lens 101 as an imaging optical system and a light receiving element 113 configured as an image sensor using a CMOS (complementary metal oxide semiconductor) imaging element or a CCD (charge coupled device) imaging element. The light receiving element 113 reads an optical image of a subject (object) formed by the photographing lens 101. As the photographing lens 101, the wide-angle lens according to the present invention as described in the first to sixth embodiments is used (corresponding to claim 9 or claim 10).

  The output of the light receiving element 113 is processed by a signal processing device 114 controlled by the central processing unit 111 and converted into digital image information. That is, such a digital camera includes means for converting a captured image (subject image) into digital image information. This means substantially controls the light receiving element 113, the signal processing device 114, and these. Central processing unit (CPU) 111 and the like.

  The image information digitized by the signal processing device 114 is recorded in a semiconductor memory 115 such as a nonvolatile memory after being subjected to predetermined image processing in the image processing device 112 which is also controlled by the central processing unit 111. In this case, the semiconductor memory 115 may be a memory card loaded in the memory card slot 109 or a semiconductor memory built in the camera body (on-board). The liquid crystal monitor 107 can display an image being photographed, or can display an image recorded in the semiconductor memory 115. The image recorded in the semiconductor memory 115 can also be transmitted to the outside via a communication card 116 or the like loaded in the communication card slot 110.

When the camera is carried, the objective surface of the photographic lens 101 is covered with a lens barrier (not shown). When the user operates the power switch 106 to turn on the power, the lens barrier is opened and the objective surface is The structure is exposed. At this time, inside the lens barrel of the photographing lens 101, the optical systems of the respective groups constituting the wide-angle lens are arranged in the photographing state.
In many cases, focusing is performed by half-pressing the shutter button 104. Focusing in the wide-angle lens according to the present invention (the wide-angle lens defined in claims 1 to 7 or shown in the first to sixth embodiments described above) is a movement of a part of a plurality of groups of optical systems. Or by moving the light receiving element. When the shutter button 104 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.

  When the image recorded in the semiconductor memory 115 is displayed on the liquid crystal monitor 107 or transmitted to the outside via the communication card 116 or the like, the operation button 108 is operated as specified. The semiconductor memory 115 and the communication card 116 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 109 and the communication card slot 110, respectively.

  As described above, the above-described digital camera (imaging device) or portable information terminal device captures the photographing lens 101 configured using the wide-angle lens as described in the first to sixth embodiments. It can be used as an optical system. Therefore, it is possible to realize a small digital camera (imaging device) or portable information terminal device that has high resolving power and is stable with respect to environmental fluctuations.

  Moreover, it is also suitable as an imaging lens for a vehicle-mounted camera, a surveillance camera, or the like.

G1 Front lens group G2 Rear lens group L1, L2, L3, L4, L5, L6, L7 First lens, second lens, third lens, fourth lens, fifth lens, sixth lens, seventh lens AD Optics Aperture FT Parallel plate 101 Photo lens 102 Optical viewfinder 103 Strobe (flashlight)
104 Shutter button 105 Camera body 106 Power switch 107 Liquid crystal monitor 108 Operation button 109 Memory card slot 110 Communication card slot 111 Central processing unit (CPU)
112 Image processing device 113 Light receiving element 114 Signal processing device 115 Semiconductor memory 116 Communication card etc.

Japanese Patent No. 2992547 JP 2010-009028 A JP 2002-072085 A

Claims (10)

In order from the object side to the image side, a front group lens, an optical diaphragm, and a rear group lens are configured. The front group lens is sequentially arranged from the object side to the image side, a meniscus negative first lens, and plastic. A negative second lens having an aspherical surface and a positive third lens, and the rear lens group is a positive fourth lens, a positive fifth lens, and a negative sixth lens in order from the object side to the image side. A wide-angle lens composed of a positive seventh lens made of plastic and having an aspheric surface ,
Of the four positive lenses, two positive glass lenses satisfy the following conditional expression (1):
−3.7 × 10 ⁻⁶ <dN / dT <−2.2 × 10 ⁻⁶ (1)
However, dN / dT represents the refractive index change rate of the d-line with respect to the temperature change near room temperature. In order from the object side to the image side, a front group lens, an optical diaphragm, and a rear group lens are configured. The front group lens is sequentially arranged from the object side to the image side, a meniscus negative first lens, and plastic. A negative second lens having an aspherical surface and a positive third lens, and the rear lens group is a positive fourth lens, a positive fifth lens, and a negative sixth lens in order from the object side to the image side. A wide-angle lens composed of a positive seventh lens made of plastic and having an aspheric surface ,
A wide-angle lens satisfying the following conditional expression (2):
−0.9 <fn / fp <−0.7 (2)
Here, fn represents the focal length of the second lens made of a negative plastic lens having an aspheric surface, and fp represents the focal length of the seventh lens made of a positive plastic lens having an aspheric surface. The wide-angle lens according to claim 1 , wherein the following conditional expression (2) is satisfied.
A wide-angle lens satisfying the following conditional expression (2):
−0.9 <fn / fp <−0.7 (2)
Here, fn represents the focal length of the second lens made of a negative plastic lens having an aspheric surface, and fp represents the focal length of the seventh lens made of a positive plastic lens having an aspheric surface. 4. The wide-angle lens according to claim 1, wherein the wide-angle lens satisfies the following conditional expression (3): 5.
-2.3 <fn / f < -1.8 (3)
However, fn represents the focal length of the negative second lens having an aspheric surface, and f represents the focal length of the entire system. The wide-angle lens according to any one of claims 1 to 4, wherein the wide-angle lens satisfies the following conditional expression (4).
1.6 <H2 / R2 <1.8 (4)
However, H2 represents the effective diameter on the image side surface of the negative first lens, and R2 represents the radius of curvature of the image side surface of the negative first lens. The wide-angle lens according to any one of claims 1 to 5, wherein the positive fifth lens and the negative sixth lens are cemented lenses, and satisfy the following conditional expression (5): A featured wide-angle lens.
-4.0 <fc / fR <-1.9 (5)
However, fc represents the focal length of the cemented lens composed of the positive fifth lens and the negative sixth lens, and fR represents the focal length of the rear lens group. The wide-angle lens according to claim 1, wherein the wide-angle lens satisfies the following conditional expression (6).
−1.3 <f12 / f <−1.0 (6)
However, f12 represents the combined focal length of the first lens and the second lens, and f represents the focal length of the entire system.   An imaging lens unit comprising the wide-angle lens according to any one of claims 1 to 7 as an optical system.   An imaging apparatus comprising the wide-angle lens according to claim 1 as an imaging optical system.   An information apparatus using the wide-angle lens according to any one of claims 1 to 7 as an imaging optical system.

Images